Compounds of formula 
wherein R1 is hydrogen or a lower alkyl radical and n is 4, 5, or 6 are known in U.S. Pat. No. 4,024,175 and its divisional U.S. Pat. No. 4,087,544. The uses disclosed are: protective effect against cramp induced by thiosemicarbazide; protective action against cardiazole cramp; the cerebral diseases, epilepsy, faintness attacks, hypokinesia, and cranial traumas; and improvement in cerebral functions. The compounds are useful in geriatric patients. The patents are hereby incorporated by reference.
The instant invention is a series of novel bicyclic amino acids, their pharmaceutically acceptable salts, and the prodrugs of the amino acids.
The compounds are those of formula: 
wherein n is an integer of from 1 to 4, where there are stereocenters, each center may be independently R or S.
Preferred compounds of the invention are those of Formulae I-IV above wherein n is an integer of from 2 to 4.
Other preferred compounds are those of Formula I above.
Especially preferred compounds are:
(1xcex1,6xcex1,8xcex2)(2-Aminomethyl-octahydro-inden-2-yl)-acetic acid;
(2-Aminomethyl-octahydro-inden-2-yl)-acetic acid;
(2-Aminomethyl-octahydro-pentalen-2-yl)-acetic acid;
(2-Aminomethyl-octahydro-pentalen-2-yl)-acetic acid;
(3-Aminomethyl-bicyclo[3.2.0]hept-3-yl)-acetic acid;
(3-Aminomethyl-bicyclo[3.2.0]hept-3-yl)-acetic acid; and
(2-Aminomethyl-octahydro-inden-2-yl)-acetic acid.
Other preferred compounds are those selected from
(1xcex1,5xcex2)(3-Aminomethyl-bicyclo[3.1.0]hex-3-yl)-acetic acid,
(1xcex1,5xcex2)(3-Aminomethyl-bicyclo[3.2.0]hept-3-yl)-acetic acid,
(1xcex1,5xcex2)(2-Aminomethyl-octahydro-pentalen-2-yl)-acetic acid,
(1xcex1,6xcex2)(2-Aminomethyl-octahydro-inden-2-yl)-acetic acid,
(1xcex1,7xcex2)(2-Aminomethyl-decahydro-azulen-2-yl)-acetic acid,
(1xcex1,5xcex2)(3-Aminomethyl-bicyclo[3.1.0]hex-3-yl)-acetic acid,
(1xcex1,5xcex2)(3-Aminomethyl-bicyclo[3.2.0]hept-3-yl)-acetic acid,
(1xcex1,5xcex2)(2-Aminomethyl-octahydro-pentalen-2-yl)-acetic acid,
(1xcex1,6xcex2)(2-Aminomethyl-octahydro-inden-2-yl)-acetic acid,
(1xcex1,7xcex2)(2-Aminomethyl-decahydro-azulen-2-yl)-acetic acid,
(1xcex1,3xcex1,5xcex1)(3-Aminomethyl-bicyclo[3.1.0]hex-3-yl)-acetic acid,
(1xcex1,3xcex1,5xcex1)(3-Aminomethyl-bicyclo[3.2.0]hept-3-yl)-acetic acid,
(1xcex1,3xcex1,5xcex1)(2-Aminomethyl-octahydro-pentalen-2-yl)-acetic acid,
(1xcex1,6xcex1,8xcex1)(2-Aminomethyl-octahydro-inden-2-yl)-acetic acid,
(1xcex1,7xcex1,9xcex1)(2-Aminomethyl-decahydro-azulen-2-yl)-acetic acid,
(1xcex1,3xcex2,5xcex1)(3-Aminomethyl-bicyclo[3.1.0]hex-3-yl)-acetic acid,
(1xcex1,3xcex2,5xcex1)(3-Aminomethyl-bicyclo[3.2.0]hept-3-yl)-acetic acid,
(1xcex1,3xcex2,5xcex1)(2-Aminomethyl-octahydro-pentalen-2-yl)-acetic acid,
(1xcex1,6xcex1,8xcex2)(2-Aminomethyl-octahydro-inden-2-yl)-acetic acid,
(1xcex1,7xcex1,9xcex2)(2-Aminomethyl-decahydro-azulen-2-yl)-acetic acid,
((1R,3R,6R)-3-Aminomethyl-bicyclo[4.1.0]hept-3-yl)-acetic acid,
((1R,3S,6R)-3-Aminomethyl-bicyclo[4.1.0]hept-3-yl)-acetic acid,
((1S,3S,6S)-3-Aminomethyl-bicyclo[4.1.0]hept-3-yl)-acetic acid,
((1S,3R,6S)-3-Aminomethyl-bicyclo[4.1.0]hept-3-yl)-acetic acid,
((1R,3R,6S)-3-Aminomethyl-bicyclo[4.2.0]oct-3-yl)-acetic acid,
((1R,3S,6S)-3-Aminomethyl-bicyclo[4.2.0]oct-3-yl)-acetic acid,
((1S,3S,6R)-3-Aminomethyl-bicyclo[4.2.0]oct-3-yl)-acetic acid,
((1S,3R,6R)-3-Aminomethyl-bicyclo[4.2.0]oct-3-yl)-acetic acid,
((3xcex1R,5R,7xcex1S)-5-Aminomethyl-octahydro-inden-5-yl)-acetic acid,
((3xcex1R,5S,7xcex1S)-5-Aminomethyl-octahydro-inden-5-yl)-acetic acid,
((3xcex1S,5S,7xcex1R)-5-Aminomethyl-octahydro-inden-5-yl)-acetic acid,
((3xcex1S,5R,7xcex1R)-5-Aminomethyl-octahydro-inden-5-yl)-acetic acid,
((2R,4xcex1S,8xcex1R)-2-Aminomethyl-decahydro-naphthalen-2-yl)-acetic acid,
((2S,4xcex1S,8xcex1R)-2-Aminomethyl-decahydro-naphthalen-2-yl)-acetic acid,
((2S,4xcex1S,8xcex1S)-2-Aminomethyl-decahydro-naphthalen-2-yl)-acetic acid,
((2R,4xcex1R,8xcex1S)-2-Aminomethyl-decahydro-naphthalen-2-yl)-acetic acid,
((2R,4xcex1S,9xcex1R)-2-Aminomethyl-decahydro-benzocyclophepten-2-yl)-acetic acid,
((2S,4xcex1S,9xcex1R)-2-Aminomethyl-decahydro-benzocyclophepten-2-yl)-acetic acid,
((2S,4xcex1R,9xcex1S)-2-Aminomethyl-decahydro-benzocyclophepten-2-yl)-acetic acid,
((2R,4xcex1R,9xcex1S)-2-Aminomethyl-decahydro-benzocyclophepten-2-yl)-acetic acid,
((1R,3R,6S)-3-Aminomethyl-bicyclo[4.1.0]hept-3-yl)-acetic acid,
((1R,3S,6S)-3-Aminomethyl-bicyclo[4.1.0]hept-3-yl)-acetic acid,
((1S,3S,6R)-3-Aminomethyl-bicyclo[4.1.0]hept-3-yl)-acetic acid,
((1S,3R,6R)-3-Aminomethyl-bicyclo[4.1.0]hept-3-yl)-acetic acid,
((1R,3R,6R)-3-Aminomethyl-bicyclo[4.2.0]oct-3-yl)-acetic acid,
((1R,3S,6R)-3-Aminomethyl-bicyclo[4.2.0]oct-3-yl)-acetic acid,
((1S,3S,6S)-3-Aminomethyl-bicyclo[4.2.0]oct-3-yl)-acetic acid,
((1S,3R,6S)-3-Aminomethyl-bicyclo[4.2.0]oct-3-yl)-acetic acid,
((3xcex1R,5R,7xcex1R)-5-Aminomethyl-octahydro-inden-5-yl)-acetic acid,
((3xcex1R,5S,7xcex1R)-5-Aminomethyl-octahydro-inden-5-yl)-acetic acid,
((3xcex1S,5S,7xcex1S)-5-Aminomethyl-octahydro-inden-5-yl)-acetic acid,
((3xcex1S,5R,7xcex1S)-5-Aminomethyl-octahydro-inden-5-yl)-acetic acid,
((2R,4xcex1R,8xcex1R)-2-Aminomethyl-decahydro-naphthalen-2-yl)-acetic acid,
((2S,4xcex1S,8xcex1R)-2-Aminomethyl-decahydro-naphthalen-2-yl)-acetic acid,
((2S,4xcex1R,8xcex1S)-2-Aminomethyl-decahydro-naphthalen-2-yl)-acetic acid,
((2R,4xcex1S,8xcex1S)-2-Aminomethyl-decahydro-naphthalen-2-yl)-acetic acid,
((2R,4xcex1R,9xcex1R)-2-Aminomethyl-decahydro-benzocyclophepten-2-yl)-acetic acid,
((2S,4xcex1R,9xcex1R)-2-Aminomethyl-decahydro-benzocyclophepten-2-yl)-acetic acid,
((2S,4xcex1S,9xcex1S)-2-Aminomethyl-decahydro-benzocyclophepten-2-yl)-acetic acid, and
((2R,4xcex1S,9xcex1S)-2-Aminomethyl-decahydro-benzocyclophepten-2-yl)-acetic acid.
The compounds of the invention are useful in treating a variety of disorders. The disorders include: epilepsy, faintness attacks, hypokinesia, cranial disorders, neurodegenerative disorders, depression, anxiety, panic, pain, neuropathological disorders, and sleep disorders.
Intermediates useful in the preparation of the final products are also included in the scope of the invention.
The compounds of the instant invention, their prodrugs, and their pharmaceutically acceptable salts are as defined above in Formulae I-IV.
Pharmaceutical compositions comprising a therapeutically effective amount of a compound of Formulas I-VII above are included in the instant invention.
Methods of using the compounds of the invention as agents for treating epilepsy, faintness attacks, hypokinesia, cranial disorders, neurodegenerative disorders, depression, anxiety, panic, pain, neuropathological disorders, sleep disorders, and premenstrual syndrome are part of the invention.
Since amino acids are amphoteric, pharmacologically compatible salts when R is hydrogen can be salts of appropriate inorganic or organic acids, for example, hydrochloric, sulphuric, phosphoric, acetic, oxalic, lactic, citric, malic, salicylic, malonic, maleic, succinic, and ascorbic. Starting from corresponding hydroxides or carbonates, salts with alkali metals or alkaline earth metals, for example, sodium, potassium, magnesium, or calcium are formed. Salts with quaternary ammonium ions can also be prepared with, for example, the tetramethyl-ammonium ion.
Prodrugs of compounds I-VIII are included in the scope of the instant invention. Aminoacyl-glycolic and -lactic esters are known as prodrugs of amino acids (Wermuth C. G., Chemistry and Industry, 1980:433-435). The carbonyl group of the amino acids can be esterified by known means. Prodrugs and soft drugs are known in the art (Palomino E., Drugs of the Future, 1990;15(4):361-368). The last two citations are hereby incorporated by reference.
The effectiveness of an orally administered drug is dependent upon the drug""s efficient transport across the mucosal epithelium and its stability in entero-hepatic circulation. Drugs that are effective after parenteral administration but less effective orally, or whose plasma half-life is considered too short, may be chemically modified into a prodrug form.
A prodrug is a drug which has been chemically modified and may be biologically inactive at its site of action, but which may be degraded or modified by one or more enzymatic or other in vivo processes to the parent bioactive form.
This chemically modified drug, or prodrug, should have a different pharmacokinetic profile to the parent, enabling easier absorption across the mucosal epithelium, better salt formulation and/or solubility, improved systemic stability (for an increase in plasma half-life, for example). These chemical modifications may be
1) ester or amide derivatives which may be cleaved by, for example, esterases or lipases. For ester derivatives, the ester is derived from the carboxylic acid moiety of the drug molecule by known means. For amide derivatives, the amide may be derived from the carboxylic acid moiety or the amine moiety of the drug molecule by known means.
2) peptides which may be recognized by specific or nonspecific proteinases. A peptide may be coupled to the drug molecule via amide bond formation with the amine or carboxylic acid moiety of the drug molecule by known means.
3) derivatives that accumulate at a site of action through membrane selection of a prodrug form or modified prodrug form,
4) any combination of 1 to 3.
Current research in animal experiments has shown that the oral absorption of certain drugs may be increased by the preparation of xe2x80x9csoftxe2x80x9d quatemary salts. The quaternary salt is termed a xe2x80x9csoftxe2x80x9d quatemary salt since, unlike normal quaternary salts, e.g., Rxe2x80x94N+(CH3)3, it can release the active drug on hydrolysis.
xe2x80x9cSoftxe2x80x9d quatemary salts have useful physical properties compared with the basic drug or its salts. Water solubility may be increased compared with other salts, such as the hydrochloride, but more important there may be an increased absorption of the drug from the intestine. Increased absorption is probably due to the fact that the xe2x80x9csoftxe2x80x9d quatemary salt has surfactant properties and is capable of forming micelles and unionized ion pairs with bile acids, etc., which are able to penetrate the intestinal epithelium more effectively. The prodrug, after absorption, is rapidly hydrolyzed with release of the active parent drug.
Certain of the compounds of the present invention can exist in unsolvated forms as well as solvated forms, including hydrated forms. In general, the solvated forms, including hydrated forms, are equivalent to unsolvated forms and are intended to be encompassed within the scope of the present invention.
Certain of the compounds of the present invention possess one or more chiral centers and each center may exist in the R(D) or S(L) configuration. The present invention includes all enantiomeric and epimeric forms as well as the appropriate mixtures thereof. For example, the compound of Example 2 is a mixture of all four possible stereoisomers. The compound of Example 6 is one of the isomers. The configuration of the cyclohexane ring carbon centers may be R or S in these compounds where a configuration can be defined.
The radioligand binding assay using [3H]gabapentin and the xcex12xcex4 subunit derived from porcine brain tissue was used (Gee N. S., Brown J. P., Dissanayake V. U. K., Offord J., Thurlow R., Woodruff G. N., xe2x80x9cThe Novel Anti-convulsant Drug, Gabapentin, Binds to the xcex12xcex4 Subunit of a Calcium Channel,xe2x80x9d J. Biol. Chem., 1996;271:5879-5776).
Table 1 above shows the binding affinity of the compounds of the invention to the xcex12xcex4 subunit.
The compounds of the invention are compared to Neurontin(copyright), a marketed drug effective in the treatment of such disorders as epilepsy. Neurontin(copyright) is 1-aminomethyl)-cyclohexaneacetic acid of structural formula 
Gabapentin (Neurontin(copyright)) is about 0.10 to 0.12 xcexcM in this assay. The compounds of the instant invention are expected, therefore, to exhibit pharmacologic properties comparable to gabapentin. For example, as agents for the treatment of convulsions, anxiety, and pain.
The present invention also relates to therapeutic use of the compounds of the mimetic as agents for neurodegenerative disorders.
Such neurodegenerative disorders are, for example, Alzheimer""s disease, Huntington""s disease, Parkinson""s disease, and Amyotrophic Lateral Sclerosis.
The present invention also covers treating neurodegenerative disorders termed acute brain injury. These include but are not limited to: stroke, head trauma, and asphyxia
Stroke refers to a cerebral vascular disease and may also be referred to as a cerebral vascular incident (CVA) and includes acute thromboembolic stroke. Stroke includes both focal and global ischemia Also, included are transient cerebral ischemic attacks and other cerebral vascular problems accompanied by cerebral ischemnia. A patient undergoing carotid endarterectomy specifically or other cerebrovascular or vascular surgical procedures in general, or diagnostic vascular procedures including cerebral angiography and the like.
Other incidents are head trauma, spinal cord trauma, or injury from general anoxia, hypoxia, hypoglycemia, hypotension as well as similar injuries seen during procedures from embole, hyperfusion, and hypoxia.
The instant invention would be useful in a range of incidents, for example, during cardiac bypass surgery, in incidents of intracranial hemorrhage, in perinatal asphyxia, in cardiac arrest, and status epilepticus.
Pain refers to acute as well as chronic pain.
Acute pain is usually short-lived and is associated with hyperactivity of the sympathetic nervous system. Examples are postoperative pain and allodynia.
Chronic pain is usually defined as pain persisting from 3 to 6 months and includes somatogenic pains and psychogenic pains. Other pain is nociceptive.
Still other pain is caused by injury or infection of peripheral sensory nerves. It includes, but is not limited to pain from peripheral nerve trauma, herpes virus infection, diabetes mellitus, causalgia, plexus avulsion, neuroma, limb amputation, and vasculitis. Neuropathic pain is also caused by nerve damage from chronic-alcoholism, human immunodeficiency virus infection, hypothyroidism, uremia, or vitamin deficiencies. Neuropathic pain includes, but is not limited to pain caused by nerve injury such as, for example, the pain diabetics suffer from.
Psychogenic pain is that which occurs without an organic origin such as low back pain, atypical facial pain, and chronic headache.
Other types of pain are: inflammatory pain, osteoarthritic pain, trigeminal neuralgia, cancer pain, diabetic neuropathy, restless leg syndrome, acute herpetic and postherpetic neuralgia, causalgia, brachial plexus avulsion, occipital neuralgia, gout, phantom limb, burn, and other forms of neuralgia, neuropathic and idiopathic pain syndrome.
A skilled physician will be able to determine the appropriate situation in which subjects are susceptible to or at risk of, for example, stroke as well as suffering from stroke for administration by methods of the present invention.
The compounds of the invention are also expected to be useful in the treatment of depression. Depression can be the result of organic disease, secondary to stress associated with personal loss, or idiopathic in origin. There is a strong tendency for familial occurrence of some forms of depression suggesting a mechanistic cause for at least some forms of depression. The diagnosis of depression is made primarily by quantification of alterations in patients"" mood. These evaluations of mood are generally performed by a physician or quantified by a neuropsychologist using validated rating scales, such as the Hamilton Depression Rating Scale or the Brief Psychiatric Rating Scale. Numerous other scales have been developed to quantify and measure the degree of mood alterations in patients with depression, such as insomnia, difficulty with concentration, lack of energy, feelings of worthlessness, and guilt. The standards for diagnosis of depression as well as all psychiatric diagnoses are collected in the Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) referred to as the DSM-IV-R manual published by the American Psychiatric Association, 1994.
GABA is an inhibitory neurotransmitter with the central nervous system. Within the general context of inhibition, it seems likely that GABA-mimetics might decrease or inhibit cerebral function and might therefore slow function and decrease mood leading to depression.
The compounds of the instant invention may produce an anticonvulsant effect through the increase of newly created GABA at the synaptic junction. If gabapentin does indeed increase GABA levels or the effectiveness of GABA at the synaptic junction, then it could be classified as a GABA-mimetic and might decrease or inhibit cerebral function and might, therefore, slow function and decrease mood leading to depression.
The fact that a GABA agonist or GABA-mimetic might work just the opposite way by increasing mood and thus, be an antidepressant, is a new concept, different from the prevailing opinion of GABA activity heretofore.
The compounds of the instant invention are also expected to be useful in the treatment of anxiety and of panic as demonstrated by means of standard pharmacological procedures.
Nociceptive pressure thresholds were measured in the rat paw pressure test using an analgesimeter (Randall-Selitto method: Randall L. O. and Selitto J. J., xe2x80x9cA method for measurement of analgesic activity on inflamed tissue,xe2x80x9d Arch. Int. Pharmacodyn., 1957;4:409-419). Male Sprague-Dawley rats (70-90 g) were trained on this apparatus before the test day. Pressure was gradually applied to the hind paw of each rat and nociceptive thresholds were determined as the pressure (g) required to elicit paw withdrawal. A cutoff point of 250 g was used to prevent any tissue damage to the paw. On the test day, two to three baseline measurements were taken before animals were administered 100 xcexcL of 2% carrageenin by intraplantar injection into the right hind paw. Nociceptive thresholds were taken again 3 hours after carrageenin to establish that animals were exhibiting hyperalgesia. Animals were dosed with either gabapentin (3-300 mg, s.c.), morphine (3 mg/kg, s.c.) or saline at 3.5 hours after carrageenin and nociceptive thresholds were examined at 4, 4.5, and 5 hours postcarrageenin.
(R)-2-Aza-spiro[4.5]decane-4-carboxylic acid hydrochloride was tested in the above carrageenan-induced hyperalgesia model. The compound was dosed orally at 30 mg/kg, and 1 hour postdose gave a percent of maximum possible effect (MPE) of 53%. At 2 hours postdose, it gave only 4.6% of MPE.
Tonic seizures in mice are induced by subcutaneous administration of semicarbazide (750 mg/kg). The latency to the tonic extension of forepaws is noted. Any mice not convulsing within 2 hours after semicarbazide are considered protected and given a maximum latency score of 120 minutes.
Male Hooded Lister rats (200-250 g) are obtained from Interfauna (Huntingdon, UK) and male TO mice (20-25 g) are obtained from Bantin and Kingman (Hull, UK). Both rodent species are housed in groups of six. Ten Common Marmosets (Callithrix Jacchus) weighing between 280 and 360 g, bred at Manchester University Medical School (Manchester, UK) are housed in pairs. All animals are housed under a 12-hour light/dark cycle (lights on at 07.00 hour) and with food and water ad libitum.
Drugs are administered either intraperitoneally (IP) or subcutaneously (SC) 40 minutes before the test in a volume of 1 mL/kg for rats and marmosets and 10 mL/kg for mice.
The apparatus is an open-topped box, 45 cm long, 27 cm wide, and 27 cm high, divided into a small (2/5) and a large (3/5) area by a partition that extended 20 cm above the walls (Costall B., et at., xe2x80x9cExploration of mice in a black and white box: validation as a model of anxiety,xe2x80x9d Pharmacol. Biochem. Behav., 1989;32:777-785).
There is a 7.5xc3x977.5 cm opening in the center of the partition at floor level. The small compartment is painted black and the large compartment white. The white compartment is illuminated by a 60-W tungsten bulb. The laboratory is illuminated by red light. Each mouse is tested by placing it in the center of the white area and allowing it to explore the novel environment for 5 minutes. The time spent in the illuminated side is measured (Kilfoil T., et al., xe2x80x9cEffects of anxiolytic and anxiogenic drugs on exploratory activity in a simple model of anxiety in mice,xe2x80x9d Neuropharmacol., 1989;28:901-905).
A standard elevated X-maze (Handley S. L., et al., xe2x80x9cEffects of alpha-adrenoceptor agonists and antagonists in a maze-exploration model of xe2x80x98fearxe2x80x99-motivated behavior,xe2x80x9d NaunynSchiedeberg""s Arch. Pharmacol., 1984;327:1-5), was automated as previously described (Field, et al., xe2x80x9cAutomation of the rat elevated X-maze test of anxiety,xe2x80x9d Br. J. Pharmacol., 1991;102(Suppl.):304P). The animals are placed on the center of the X-maze facing one of the open arms. For determining anxiolytic effects the entries and time spent on the end half sections of the open arms is measured during the 5-minute test period (Costall, et al., xe2x80x9cUse of the elevated plus maze to assess anxiolytic potential in the rat,xe2x80x9d Br. J. Pharmacol., 1989;96(Suppl.):312p).
The total number of body postures exhibited by the animal towards the threat stimulus (a human standing approximately 0.5 m away from the marmoset cage and staring into the eyes of the marmoset) is recorded during the 2-minute test period. The body postures scored are slit stares, tail postures, scent marking of the cage/perches, piloerection, retreats, and arching of the back. Each animal is exposed to the threat stimulus twice on the test day before and after drug treatment The difference between the two scores is analyzed using one-way analysis of variance followed by Dunnett""s t-test. All drug treatments are carried out SC at least 2 hours after the first (control) threat. The pretreatment time for each compound is 40 minutes.
Rats are trained to press levers for food reward in operant chambers. The schedule consists of alternations of four 4-minute unpunished periods on variable interval of 30 seconds signaled by chamber lights on and three 3-minute punished periods on fixed ratio 5 (by footshock concomitant to food delivery) signaled by chamber lights off. The degree of footshock is adjusted for each rat to obtain approximately 80% to 90% suppression of responding in comparison with unpunished responding. Rats receive saline vehicle on training days.
All procedures were carried out in compliance with the NIH Guide for the Care and Use of Laboratory Animals under a protocol approved by the Parke-Davis Animal Use Committee. Male DBA/2 mice, 3 to 4 weeks old were obtained from Jackson Laboratories, Bar Harbour, Me. Immediately before anticonvulsant testing, mice were placed upon a wire mesh, 4 inches square, suspended from a steel rod. The square was slowly inverted through 180xc2x0 and mice observed for 30 seconds. Any mouse falling from the wire mesh was scored as ataxic (Coughenour L. L., McLean J. R., Parker R. B., xe2x80x9cA new device for the rapid measurement of impaired motor function in mice,xe2x80x9d Pharm. Biochem. Behav., 1977;6(3):351-3). Mice were placed into an enclosed acrylic plastic chamber (21 cm height, approximately 30 cm diameter) with a high-frequency speaker (4 cm diameter) in the center of the top lid. An audio signal generator (Protek model B-810) was used to produce a continuous sinusoidal tone that was swept linearly in frequency between 8 kHz and 16 kHz once each 10 msec. The average sound pressure level (SPL) during stimulation was approximately 100 dB at the floor of the chamber. Mice were placed within the chamber and allowed to acclimatize for one minute. DBA/2 mice in the vehicle-treated group responded to the sound stimulus (applied until tonic extension occurred, or for a maximum of 60 sec) with a characteristic seizure sequence consisting of wild running followed by clonic seizures, and later by tonic extension, and finally by respiratory arrest and death in 80% or more of the mice. In vehicle-treated mice, the entire sequence of seizures to respiratory arrest lasts approximately 15 to 20 seconds. The incidence of all the seizure phases in the drug-treated and vehicle-treated mice was recorded, and the occurrence of tonic seizures were used for calculating anticonvulsant ED50 values by probit analysis (Litchfield J. T., Wilcoxon F. xe2x80x9cA simplified method for evaluating dose-effect experiments,xe2x80x9d J. Pharmacol., 1949;96:99-113). Mice were used only once for testing at each dose point. Groups of DBA/2 mice (n=5-10 per dose) were tested for sound-induced seizure responses 2 hours (previously determined time of peak effect) after given drug orally. All drugs in the present study were dissolved in distilled water and given by oral gavage in a volume of 10 mL/kg of body weight. Compounds that are insoluble will be suspended in 1% carboxymethocellulose. Doses are expressed as weight of the active drug moiety.
The compounds of the instant invention are also expected to be useful in the treatment of pain and phobic disorders (Am. J. Pain Manag., 1995;5:7-9).
The compounds of the instant invention are also expected to be useful in treating the symptoms of manic, acute or chronic, single upside, or recurring depression. They are also expected to be useful in treating and/or preventing bipolar disorder (U.S. Pat. No. 5,510,381).
The compounds of the present invention can be prepared and administered in a wide variety of oral and parenteral dosage forms. Thus, the compounds of the present invention can be administered by injection, that is, intravenously, intramuscularly, intracutaneously, subcutaneously, intraduodenally, or intraperitoneally. Also, the compounds of the present invention can be administered by inhalation, for example, intranasally. Additionally, the compounds of the present invention can be administered transdermally. It will be obvious to those skilled in the art that the following dosage forms may comprise as the active component, either a compound of Formula I or a corresponding pharmaceutically acceptable salt of a compound of Formula I.
For preparing pharmaceutical compositions from the compounds of the present invention, pharmaceutically acceptable carriers can be either solid or liquid. Solid form preparations include powders, tablets, pills, capsules, cachets, suppositories, and dispersible granules. A solid carrier can be one or more substances which may also act as diluents, flavoring agents, binders, preservatives, tablet disintegrating agents, or an encapsulating material.
In powders, the carrier is a finely divided solid which is in a mixture with the finely divided active component.
In tablets, the active component is mixed with the carrier having the necessary binding properties in suitable proportions and compacted in the shape and size desired.
The powders and tablets preferably contain from five or ten to about seventy percent of the active compound. Suitable carriers are magnesium carbonate, magnesium stearate, talc, sugar, lactose, pectin, dextrin, starch, gelatin, tragacanth, methylcellulose, sodium carboxymethylcellulose, a low melting wax, cocoa butter, and the like. The term xe2x80x9cpreparationxe2x80x9d is intended to include the formulation of the active compound with encapsulating material as a carrier providing a capsule in which the active component with or without other carriers, is surrounded by a carrier, which is thus in association with it. Similarly, cachets and lozenges are included. Tablets, powders, capsules, pills, cachets, and lozenges can be used as solid dosage forms suitable for oral administration.
For preparing suppositories, a low melting wax, such as a mixture of fatty acid glycerides or cocoa butter, is first melted and the active component is dispersed homogeneously therein, as by stirring. The molten homogenous mixture is then poured into convenient sized molds, allowed to cool, and thereby to solidify.
Liquid form preparations include solutions, suspensions, and emulsions, for example, water or water propylene glycol solutions. For parenteral injection liquid preparations can be formulated in solution in aqueous polyethylene glycol solution.
Aqueous solutions suitable for oral use can be prepared by dissolving the active component in water and adding suitable colorants, flavors, stabilizing and thickening agents as desired.
Aqueous suspensions suitable for oral use can be made by dispersing the finely divided active component in water with viscous material, such as natural or synthetic guns, resins, methylcellulose, sodium carboxymethylcellulose, and other well-known suspending agents.
Also included are solid form preparations which are intended to be converted, shortly before use, to liquid form preparations for oral administration. Such liquid forms include solutions, suspensions, and emulsions. These preparations may contain, in addition to the active component, colorants, flavors, stabilizers, buffers, artificial and natural sweeteners, dispersants, thickeners, solubilizing agents, and the like.
The pharmaceutical preparation is preferably in unit dosage form. In such form the preparation is subdivided into unit doses containing appropriate quantities of the active component. The unit dosage form can be a packaged preparation, the package containing discrete quantities of preparation, such as packeted tablets, capsules, and powders in vials or ampoules. Also, the unit dosage form can be a capsules, tablet, cachet, or lozenge itself, or it can be the appropriate number of any of these in packaged form.
The quantity of active component in a unit dose preparation may be varied or adjusted from 0.1 mg to 1 g according to the particular application and the potency of the active component. In medical use the drug may be administered three times daily as, for example, capsules of 100 or 300 mg. The composition can, if desired, also contain other compatible therapeutic agents.
In therapeutic use, the compounds utilized in the pharmaceutical method of this invention are administered at the initial dosage of about 0.01 mg to about 100 mg/kg daily. A daily dose range of about 0.01 mg to about 100 mg/kg is preferred. The dosages, however, may be varied depending upon the requirements of the patient, the severity of the condition being treated, and the compound being employed Determination of the proper dosage for a particular situation is within the skill of the art. Generally, treatment is initiated with smaller dosages which are less than the optimum dose of the compound. Thereafter, the dosage is increased by small increments until the optimum effect under the circumstances is reached. For convenience, the total daily dosage may be divided and administered in portions during the day, if desired.